Turbine systems are widely utilized in fields such as power generation. For example, a conventional gas turbine system includes a compressor, a combustor, and a turbine. In a conventional gas turbine system, compressed air is provided from the compressor to the combustor. The air entering the combustor is mixed with fuel and combusted. Hot gases of combustion flow from the combustor to the turbine to drive the gas turbine system and generate power.
Further, in a typical arrangement, an annular array of combustors is connected to the first stage of the turbine by a plurality of transition pieces. The transition pieces are each shaped at one end to conform to respective combustor liners, and at an opposite end to conform to the inlet of the turbine. Thus, at the opposite end, a transition piece has an aft frame by which the transition piece is secured to the turbine. An impingement sleeve may surround the transition duct, and may be used to direct working fluid discharged from the compressor into contact with the transition piece. This working fluid eventually mixes with the fuel in the combustor.
Currently, some of the working fluid that enters the flow path between the transition piece and the surrounding impingement sleeve is removed through holes in the aft frame. This working fluid, which is used to cool the aft frame, dumps into the hot gas from the combustor just before the hot gas enters the turbine. The problem with this current cooling method is that this working fluid effectively bypasses mixing and combustion in the combustor, thereby effectively increasing the flame temperature and NOx emissions.
Thus, an improved aft frame and method for cooling an aft frame would be desired in the art. For example, an aft frame and a method that allow for cooling of the aft frame without dumping the fluid used to cool the aft frame directly into the hot gas would be advantageous. Further, an aft frame and a method that allow for cooling of the aft frame and then reusing the cooling fluid would be desired.